Optical wavelength division multiplexing is a known technique for combining a plurality of optical signals having different wavelengths and inserting the wavelengths into a single optical fiber. The multiple wavelength signal is transmitted through the fiber to a receiving end where the wavelengths are separated and demultiplexed accordingly. Typically, the wavelengths are multiplexed and demultiplexed by the use of diffraction gratings or thin film interference filters. These devices provide a spectral selectivity that is predetermined in accordance with the wavelengths in use.
One advantage that results from the use of wavelength division multiplexing is that a single optical fiber can simultaneously carry a plurality of data signals in two directions.
The following commonly assigned U.S. patents are all directed to optical and/or WDM communication techniques: U.S. Pat. No. 4,792,999, entitled "Wavelength Agile Optical Receiver" (Stilwell, Jr.); U.S. Pat. No. 5,040,169, entitled "Wavelength Division Photonic Switch" (Guerin et al.); and U.S. Pat. No. 5,157,530, entitled "Optical Fiber System" (Loeb et al.). Also of interest is commonly assigned European patent application A 0 279 932, entitled "Optical Communication Signal Source" (Block et al.).
Other patents of interest include the following: U.S. Pat. No. 4,343,532, entitled "Dual Directional Wavelength Demultiplexer" (Palmer); U.S. Pat. No. 4,430,700, entitled "System and Method For Communication Between Nodes of a Closed Loop Local Communication Path" (Chadima, Jr. et al.); U.S. Pat. No. 4,673,270, entitled "Channel Add/Drop Filter-Coupler" (Gordon); U.S. Pat. No. 4,824,193, entitled "Holographic Multiplexer/Demultiplexer and Its Manufacturing Method" (Maeda et al.); U.S. Pat. No. 4,941,208, entitled "High Performance Subcarrier Multiplexed Optical Communication System With Modulation Index Exceeding Unity" (Olshansky et al.); and U.S. Pat. No. 5,064,263, entitled "Multiplexing Apparatus For The Direct Optical Reception of a Plurality of Optical Wavelengths" (Stein).
A problem arises in the use of conventional multiplexing equipment when it is desired to send and receive multiple high-speed full-duplex data streams of different types. That is, a user may have one type of equipment that generates a data stream at a first bit rate and with a first communications protocol and a second type of equipment that generates a second bit stream with a second bit rate and a second communications protocol that differs from the first protocol. Typically, the user would be required to rent, at considerable cost, a pair of fiberoptic conductors from a fiber provider for each of the full-duplex data streams. As the number of different types of data communications equipment increases, it can be appreciated that the expense associated with renting additional fiber pairs may become prohibitive.